The pull bolts came right out without a hitch - they were finger tight . However the plaster took longer to dry than expected. And the mistake that caused me to have to cast a second batch of plaster resulted in the base of the casting having lots of bubbles in it (I suspect some of the water in the second batch was absorbed by the partially setting first batch which didn't allow it to expel all the bubbles produced by mixing).

When I cast the plaster I filled the mold as high as possible even though the OEM canopy had some extra material at the base. This left a flanged area that is now faired to the basic canopy contours. And the bottom has been planed fair. A Sureform file was used for basic trimming, followed by final sanding. At this point only a couple of tiny bubbles remain to be filled with spackle.

(The lightweight Hydrocal I bought for the project when my old supply of regular didn't look good is softer than I would like. So I'm going to put a coat of thinned polyester resin over the surface to help protect it against 'hangar rash'. Polyester is the better choice vs epoxy because it has better heat resistance and sets faster.)

Despite these minor irritations, the plug should work just fine.